A scanner of prior arts as shown in FIG. 1 has a main body 2, of which surface has a transparent platen 3, and inside which has an optical chassis 5 capable of repetitious displacement. A document 4 is placed on the transparent platen 3 and is covered by a cover 1, and at this time, the optical chassis 5 in the main body 2 is displaced from one side of the platen 3 to scan the data of the document 4 for picking up image, and its motion is shown in FIG. 2.
In order to obtain appropriate optical length within specific volume for above-mentioned optical chassis 5, inside which plural reflection mirrors are arranged for obtaining appropriate optical length to make the reflection light be focused into an image onto a CCD by a lens.
Please refer to FIG. 3, which shows an example that plural mirrors reflect the light to obtain appropriate optical length. In this structure, a first light source 501 irradiates a light toward a document 4, and the light is reflected toward the first mirror 502, the second mirror 503, and the third mirror 504 in sequence to be focused into an image afterwards on the first CCD 506 by the first lens 505. In this example, three reflection mirrors guide the light to obtain an appropriate optical length, thereby the volume of the optical chassis 5 is reduced, and therefore, someone applies the same principle with further more mirrors to achieve this object. Thus, following the increasing number of components, the position problem is incurred more frequently, because a supporting point is needed for each mirror. Thus, when assembling each mirror, the accumulated tolerance of each mirror makes the position for each mirror become more difficult and the malfunction for components is incurred more frequently. Furthermore, the increasing number of components will complicate the filing and stocking works for supplies relatively, and the cost of supplies is also increased, so the price competition ability for this product is weak.
In addition, although there is also a design of multi-reflection by single mirror or parallel mirrors, but it is independent between each mirror, so the fixation for the relative positions and angles between each mirror becomes a main factor to accumulate tolerance.
Accordingly, the inventor addresses an ingenious design of a module of reflection mirrors of L-shape 508 that can effectively improve above-mentioned shortcomings.